US Patent 7533217 Optical disc apparatus with interruptible write operation

An optical disc apparatus includes a buffer memory for shared use between write data and read data. Upon receipt of a write command from an external host device, a system controller stores, in a buffer memory, write data attached to the write command, and, after storing the write data, supplies the write data to an optical pickup. When a read command is received after the receipt of the write command, execution of the write command is interrupted at a predetermined time, to store read data retrieved from the optical disc in a recorded area of the buffer memory. Further, a segment of the write data is recorded, and pre-read data retrieved from the optical disc is also stored in the area of the buffer memory, to improve a data hit rate.